| 摘要 |
An energy level due to isoelectronic impurity is provided in the forbidden band of one portion of an optical waveguide in a semiconductor material by doping said portion with an isoelectronic impurity. Upon excitation, a population inversion of electrons and holes is produced in the energy level and the valence band of said portion. When a light having a wavelength corresponding to the energy difference between the level of the isoelectronic impurity and the valence band is impinged on the portion, the incident light is amplified thereby. Since the optical energy of the output is smaller than the forbidden band gap, the attenuation in the waveguide is very small. By arranging Bragg type reflectors on both side portions of the region doped with the isoelectronic impurity, a semiconductor laser having superior selection characteristics of oscillation frequency is provided and the laser beam output thereby is only slightly attenuated in the waveguide due to the fact that the output laser beam is smaller than the forbidden band.
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